Duncan mcakthur



@uiten tatrs atrnt @fitta IMPROYED DIE-STOCK FOR GETTING SGREWS.

@t ttemle maar tu it tten Natas lateut mit mating rati at tige sami.

TO ALL -WHOM IT MAY CONCFRN: f

Be it known that I, DUNCAN McARTHUR, of New Haven, in the county of New Haven, and State o f Connecticut, have invented a new Improvementin Die- Stock for Cutting`dScrews; and I do hereby declaro the following, when taken in connection with the accompanying'drawings, and the letters of reference marked thereon, to be a full, clear, and exact description of. the same, and which said drawings constitute part of this specification, and rcpresent,.in

Figure 1, an upper' face view.

Figure'Z the same, with the covering plate removed.

Figure, a similar view, with the parts removed to more clearly illustrate the operation; and in Figure 4, a section o n line :t 11:. Y

This invention is designed for the adjustment of the die in the die-plate for screw-cutting, the object being to adjust the cutting-dies to any desired diameter of the screw, and at the same time to release them from the screw when cut, and so that a continued forward movement of the plate may be had, thc dies constantly cutting a full thread. Y

To enable others to construct this improvement, I will proceed to describe the same as illustrated in the accompanying drawings.

A is the die-plate proper, provided with handles B B,in the usual manner; Within the die-plate is arranged a ring, C, having upon one side teeth a, and through the handle'B a rack, D, so that when moved from right to left, the teeth upon the rack will cause the ring C to be turned accordingly, as from-iig. 2 to iig. 3, and vice versa. The plate A extends withinthe ring C, as denoted in fig. 3, and in that portion of the plate are arranged three dies or cutters d, more or less in number, the cutting-edge`b`eing upon the forward point, as atf, and the portion of the die back of the said cutting-point formed so as to ll, or nearly so, the thread cut by the advancing cutting-edge, and thus 'form a perfect guide for thc die, and to this end the side of the die upon which the cuttingredge is formed, is in a direct radial line from thecentre of the plate, as in fig. 3. On the inner surface of the ring C are formed cams c, corresponding-to the several dies, .so that by turning the ring C, as from thel position in fig. 2 to that in iig..3, the dies are forced forward to reduce the diameter; and in.order that by returning the ring C .the dies d may be'retnrned, I arrange in connection with theiring C plate, E, denoted in color, gsf and 4, with reversed cams'f operating againsta shoulder, z', upon the, dies, causes the positive return of the dies when the ring C is returned to the position in fig. 2.

To cut a thread, place the dies upon the blank, turn the blank in the usual manner, and the dies will cut a full thread, and withoutany necessary reversing of the movement of the plate, and'whcn the-thread has been so cut, turn the ring Cto open the dios to permit their removal'irom the screw without the necessity of turning the plate therefrom. To thus open the dies, press the bar D back tol the position in g. 2, which opens the dies to their full extent. Upon thc opposite end of the raclrD, I cut a thread and tix anut, F, so that by adjusting the nut on the said bar, and returning thebar until the nut strikes the handle or shoulder g, the diameter of the thread is adjusted, as by turning the nut F further on or ofi' the said bar, thc movement of theplate C must be less or more, as the case-may be', andconsequently the diameter of the thread greater or less, and bythis arrangement of the nut F, the dies may be opened and returned to positively the same point, so that many threads may be crit by the dies of exactly the same diameter. Thus one set of dies, thus arranged in-the die-- plate, serves to cut many screws of Athe same or diierent diameters without change, but if a di'erent thread is required, simply remove the dies and' place others therein.

Having thusfully described my invention, what I claim as new and useful, and desire to secure by Letters Patent, isl The arrangement described of the ring' C, with its cams c and plate E, combined with the dies d and the adjusting-rack D, the whole constructed so as to operate in the manner herein set forth.

DUNCAN McARTHUR.

Witnesses A. J. Tnsnirs, JOHN H. SHUMWAY. 

